An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves, and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves and is transported to a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. The cleaning system includes a cleaning fan which blows air through oscillating sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a straw chopper and out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
When a harvester is moving through the field, the header must be maintained at a certain height above the ground to harvest all the crop without damaging the header. Thus, when the terrain changes, the header must be re-positioned. In a conventional harvester, the header is re-positioned using data collected, by height and/or tilt sensors, on the current pass of the harvester through the field.
For example, in combines with headers that are rigidly attached to the combine feeder house, the combine is typically equipped with a header height control (HHC) system which adjusts the height and tilt angle of the header relative to the ground. The HHC system is particularly important to prevent the header from contacting objects in the field as the combine harvests crop material and furthermore helps to keep the cutting apparatus of the header at a desired height relative to the ground in order to obtain the desired crop collection. Known HHC systems include an actuator linked to a frame of the header, sensors which detect the height and/or tilt of the cutting apparatus relative to the ground, and a controller which controls the actuator based on the sensed height and/or tilt of the cutting apparatus.
One problem with conventional header control is that the system is completely reactive, relying only on data obtained from height and/or tilt sensors on the current harvesting path of the combine. Thus, when the terrain changes too quickly, the header is often not in the correct position. This may result in lost crop (e.g., header too high) or damage to the header (e.g., header too low). Additionally, because the height control system is completely reactive, ground speed of the combine is often limited by the header position and/or relief of the terrain, and thus the operator must decide upon the speed to drive the combine so as to not miss any crop and not damage the header. The conventional system thus relies to some extent upon operator judgement in selecting the correct driving speed, thereby introducing potential operator error which can decrease the efficiency of crop collection.
What is needed in the art is a HHC system that can overcome some of the previously described disadvantages of known HHC systems.